1. Field of the Invention
The present invention relates to a valve for controlling fluids and more particularly to an injection valve for injecting fuel into a combustion chamber of an internal combustion engine.
2. Description of the Prior Art
Injection valves for injecting fuel into a combustion chamber of an internal combustion engine are known in various embodiments. For instance, such injection valves are used in conjunction with reservoir-type injection systems, in which fuel is stored in a reservoir at high pressure in order to enable injection of the fuel at a constant pressure. Such injection valves comprise multiple components, such as a retaining body, a valve plate, a throttle plate, and a nozzle body, that are disposed in succession in the axial direction of the valve. The individual components of the valve are braced against one another by means of a nozzle lock nut. By using the individual components in combination with the high pressure in reservoir-type injection systems, however, sealing problems arise that can cause leakage of fuel at the valve. To prevent fuel from escaping from the valve to the outside, for instance into the engine compartment, suitable seals are necessary. In this respect, it is known for instance to exert high pressures per unit of surface area between the individual components, to provide adequate sealing on their flat contact faces. Because of an asymmetrical arrangement of bores in the components, particularly between an actuator bore and a high-pressure bore, different rigidities in the circumferential direction result, so that so-called sweating leaks can occur. In addition, there are typically uneven places and roughness on the flat sealing faces of the individual components, which can again cause leaks. Furthermore, because of the heavy load via the high pressures per unit of surface area, deformations can occur at the sealing planes between the individual components, which can also cause a leakage of fuel.
Another known possibility for sealing off the injection valve is for instance that a sealing element, such as an O-ring, is disposed on the upper end of the nozzle lock nut. Often, for receiving the sealing element on the retaining body, a recess is provided. In this known version, however, particularly when an O-ring is used, assembly problems can arise, since during the assembly the O-ring can become twisted, as a result of which the seal can no longer be reliably assured. Moreover, because of the recess formed in the retaining body for receiving the sealing element, additional notch points are created in the valve, at which cracking can develop in the component.
In view of still higher pressure systems contemplated in the future of between 1800 and 2000 bar, the injection valve sealing problems described above will only become worse.